Wireless and wired sensors can be used in a wide variety of industries and environments. For example, wired and wireless chemical sensors can be used in process control systems to detect chemical emissions or chemical concentrations and to take appropriate actions to control a process. As another example, chemical sensors can be used in asset monitoring systems to monitor the status or condition of assets in an industrial facility or other environment. As yet another example, chemical sensors can be used to protect people against toxic gases and other hazardous or dangerous chemicals, such as carbon dioxide (CO2), ammonia (NH3), hydrogen sulfide (H2S), hydrogen gas (H2), or volatile organic compounds (VOCs) and odors.
Chemical sensors routinely include one or more sensing layers, which have properties that vary based on the presence or concentration of one or more chemicals. These varying properties can be used to detect the presence of a chemical or to measure the concentration of a chemical. Sensing layers are often formed from organic compounds that interact in a reversible way with a chemical to be detected or measured. Sensing layers can also be formed using nano-composite materials that contain a host polymer and different functionalized forms of carbon nanotubes.